Manufacturing method of a light-emitting device

ABSTRACT

A method for manufacturing a light-emitting device includes steps of: providing a substrate comprising an upper surface and a lower surface opposite to the upper surface; processing the upper surface to be an uneven surface; forming a light-emitting structure on the upper surface of the substrate; and forming a hole through the substrate by radiating a coherent laser beam to the lower surface of the substrate for a predetermined time; wherein the band gap energy of the coherent laser beam is higher than the band gap energy of the substrate thereby the substrate is etched away by the laser beam.

TECHNICAL FIELD

The application relates to a manufacturing method of a light-emitting device.

DESCRIPTION OF BACKGROUND ART

The light radiation theory of light emitting diode (LED) is to generate light from the energy released by the electron moving between an n-type semiconductor and a p-type semiconductor. Because the light radiation theory of LED is different from the incandescent light which heats the filament, the LED is called a “cold” light source. Moreover, the LED is more sustainable, longevous, light and handy, and less power-consumption, therefore it is considered as another option of the light source for the illumination markets. The LED applies to various applications like the traffic signal, backlight module, street light, and medical instruments, and is gradually replacing the traditional lighting sources.

FIG. 1 illustrates the structure of a conventional light emitting device 100 which includes a transparent substrate 10, a semiconductor stack 12 formed above the transparent substrate 10, and an electrode 14 formed above the semiconductor stack 12, wherein the semiconductor stack 12 comprises, from the top, a first conductive-type semiconductor layer 120, an active layer 122, and a second conductive-type semiconductor layer 124.

In addition, the light emitting device 100 can be further connected to other components in order to form a light emitting apparatus. FIG. 2 illustrates a conventional light emitting apparatus including a sub-mount 20 carrying an electrical circuit 202, a solder 22 formed above the sub-mount 20; wherein the light emitting device 100 is bonded to the sub-mount 20 and is electrically connected with the electrical circuit 202 on the sub-mount 20 by the solder 22, and an electric connection structure 24 that electrically connects the electrode 14 of the light emitting device 100 to the electrical circuit 202 on the sub-mount 20. The sub-mount 20 may be a lead frame or a large size mounting substrate in order to facilitate circuit design and enhance heat dissipation.

Nevertheless, because the surface of the transparent substrate 10 of the conventional light emitting device 100 as shown in FIG. 1 is substantially flat and the refractive index of the transparent substrate 10 is different from the refractive index of the external environment, the total internal reflection (TIR) occurs when a light A emitted from the active layer 122. Therefore the light extraction efficiency from the light emitting device 100 is reduced drastically.

SUMMARY OF THE DISCLOSURE

A method for manufacturing a light-emitting device includes steps of: providing a substrate comprising an upper surface and a lower surface opposite to the upper surface; processing the upper surface to be an uneven surface; forming a light-emitting structure on the upper surface of the substrate; and forming a hole through the substrate by radiating a coherent laser beam to the lower surface of the substrate for a predetermined time; wherein the band gap energy of the coherent laser beam is higher than the band gap energy of the substrate thereby the substrate is etched away by the laser beam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the structure of a conventional light emitting device.

FIG. 2 illustrates the structure of a conventional light emitting apparatus.

FIGS. 3A to 3E show a method for manufacturing a light-emitting device of a first embodiment of the present application.

FIG. 4 is a cross-sectional view of a light-emitting device of a second embodiment of the present application.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As shown in FIGS. 3A to 3E, a method for manufacturing a light-emitting device of a first embodiment of the present application is disclosed. Referring to FIG. 3A, a substrate 302 having an upper surface 302 a and a lower surface 302 b opposite to the upper surface 302 a is provided, and then the upper surface 302 a is patterned by such as ICP process to be an uneven surface. The uneven surface can include a periodic pattern having a plurality of pattern units 303 having a pitch p and a raised portion 303 a. The width w of the raised portions 303 a is about 2 μm, and the height h of the raised portion 303 a is about 1.5 μm. The material of the substrate 302 includes conductive material such as Si, SiC, GaAs, or GaP, or insulating material such as sapphire, glass, or diamond. In the embodiment, the substrate 302 is preferably insulative and has a monocrystalline structure, such as sapphire.

Referring to FIG. 3B, a light-emitting structure 312 is formed by sequentially forming a buffer layer 304, a first semiconductor layer 306, an active layer 308, and a second semiconductor layer 310 on the upper surface 302 a of the substrate 302. Each of the first semiconductor layer 306, active layer 308, and second semiconductor layer 310 can be formed in an MOCVD chamber and composed of materials such as the series of aluminum gallium indium phosphide (AlGaInP), the series of aluminum gallium indium nitride (AlGaInN), and/or the series of zinc oxide (ZnO). The active layer 308 can be configured to be a single heterostructure (SH), a double heterostructure (DH), a double-side double heterostructure (DDH), or a multi-quantum well (MQW) structure.

Referring to FIG. 3C, radiating a first coherent laser beam L₁ to the lower surface 302 b of the substrate 302 for a predetermined time to form a hole 314 through the substrate 302. The band gap energy of the first coherent laser beam L₁ is higher than the band gap energy of the substrate 302 thereby a portion of the substrate 302 is removed away by the coherent laser beam L₁. A portion of the substrate 302 is etched by the first coherent laser beam L₁ until the first coherent laser beam L₁ reaches the upper surface 302 a. A part of the first coherent laser beam L₁ becomes a non-coherent laser light L₁′ by being deflected from the direction of the first coherent laser beam L₁ during a predetermined time, and a photo-detector 4 can detect the intensity of the non-coherent laser light L₁′ to communicate to a controller (not shown) to stop radiating the coherent laser beam L₁ when the intensity of the non-coherent laser light L₁′ is detected. Mostly, the intensity of the non-coherent laser light can be detected when the first coherent laser beam reaches the uneven surface. The pitch p of each of the pattern units 303 can be equal to the wavelength of the coherent laser beam L₁, or the pitch p is smaller than the wavelength of the coherent laser beam L₁. The distance d between two adjacent pattern units 303 is smaller than the wavelength of the laser beam L₁.

Referring to FIG. 3D, radiating a second coherent laser beam L₂ for cleaning the byproducts (not shown) inside the hole 314.

Referring to FIG. 3E, a conductive structure 318 is formed in the hole 314 and electrically connected to the light-emitting structure 312, and a first contact 316 is formed on the lower surface 302 b and electrically connected to the conductive structure 318. In another embodiment, the conductive structure 318 and the first contact 316 can also form a monolithic structure by deposition, electrical plating, or chemical plating. The conductive structure 318 can fill the hole 314 for better electrical contact between the light-emitting structure 312 and the first contact 316. Further, a second contact 320 can be formed on the second semiconductor layer 310 of the light-emitting structure 312. The first contact 316 and the second contact 320 are for electrically connecting to an external device such as a submount or a package unit.

As shown in FIG. 4, a light-emitting device 300 of a second embodiment of the present application is shown. The primary difference between the present embodiment and the first embodiment is that a reflective layer 322 is formed between the lower surface 302 b and the contact 316 to reflect the emitted-light L from the active layer 308 to enhance the light extraction of the light-emitting device 300. Most of the emitted-light L passes through the upper surface 302 a of the substrate 302 to reach the reflective layer 322.

Although the present application has been explained above, it is not the limitation of the range, the sequence in practice, the material in practice, or the method in practice. Any modification or decoration for present application is not detached from the spirit and the range of such. 

What is claimed is:
 1. A method for manufacturing a light-emitting device comprising steps of: providing a substrate comprising an upper surface and a lower surface opposite to the upper surface; processing the upper surface to be an uneven surface; forming a light-emitting structure on the upper surface of the substrate; and forming a hole through the substrate by radiating a first coherent laser beam to the lower surface of the substrate for a predetermined time; wherein the band gap energy of the coherent laser beam is higher than the band gap energy of the substrate thereby a portion of the substrate is etched away by the first coherent laser beam.
 2. The method according to claim 1, further comprising forming a conductive structure in the hole and electrically connected to the light-emitting structure, and forming a first contact on the lower surface of the substrate and electrically connected to the conductive structure after forming the hole.
 3. The method according to claim 1, wherein a part of the first coherent laser beam becomes a non-coherent laser light during the predetermined time by being deflected from the direction of the first coherent laser beam.
 4. The method according to claim 1, further comprising detecting the intensity of the non-coherent laser light by a photo-detector.
 5. The method according to claim 4, further comprising stopping radiating the first coherent laser beam when the intensity of the non-coherent laser light is detected.
 6. The method according to claim 5, wherein the intensity of the non-coherent laser light is detected when the first coherent laser beam reaches the uneven surface.
 7. The method according to claim 1, wherein the uneven surface comprises a periodic pattern having plurality of pattern units having a pitch.
 8. The method according to claim 7, wherein the pitch is the same as the wavelength of the coherent laser beam.
 9. The method according to claim 7, wherein the pitch is smaller than the wavelength of the coherent laser beam.
 10. The method according to claim 7, wherein the distance between two adjacent pattern units is smaller than the wavelength of the laser beam.
 11. The method according to claim 5, further comprising cleaning the hole by a second coherent laser beam after stopping radiating the coherent laser beam.
 12. The method according to claim 1, wherein the step of forming the light-emitting structure comprising steps of forming a buffer layer on the uneven surface of the substrate, forming a first semiconductor layer on the buffer layer, forming an active layer on the first semiconductor layer, and forming a second semiconductor layer on the active layer.
 13. The method according to claim 1, further comprising forming a reflective layer on the lower surface of the substrate.
 14. The method according to claim 1, wherein the method is performed in an MOCVD chamber. 